The invention refers to a windshield washing system, especially used for motor vehicles.
It is known to insert a pipe piece of a washing liquid line into the continual axial bore of the wiper shaft or to inject the pipe piece, made from form stable plastic material directly into the bore. From the specification DE-OS 39 07 962, in which this is disclosed, it can be seen, that the pipe piece rotates with the wiper shaft, so that there is no relative motion between the pipe piece and the wiper shaft. This is an advantage, if there is a connection piece or a jet body, which is placed upon the end of the pipe piece situated at the side of the wiper arm and which moves along with the wiper arm. Consequently there is no relative motion between the pipe piece and the connection piece or the jet body, so that the point of connection can be sealed relatively easily. At the end of the wiper shaft, turned away from the wiper arm, more space is available than in the wiper arm, so that it is possible to have a connecting piece resting as well, relative to the pipe piece swinging in pendular motion along with the wiper shaft, in order to compensate the pendulum movement of a pipe union at the connecting piece by a flexible hose.
If the pipe is provided only with one channel, it is advantageous to arrange the pipe piece in the wiper shaft non-rotatably with respect to the wiper shaft, however, in order to control the washing liquid this is not absolutely necessary. It is different however, if the pipe piece comprises two channels, through which the different washing jets are supplied with washing liquid in a certain time sequence. If the pipe piece turns itself inside the wiper shaft, without the connecting piece or pieces rotating along with the wiper shaft, this may lead to a connection of both channels, or also to a supply with washing fluid which supply is contrary to the requested supply of the washing jets. It turned out, that in the windshield washing system shown in the German specification DE-OS 39 07 962 the protection against twisting between the wiper shaft and the washing liquid line is not guaranteed.
From the German patent application DE-OS 36 43 476, a windshield washing system in the form of a so-called reciprocating stroke wiper system is known, in which a washing liquid line integrally comprises a pipe piece with two channels guided through the wiper shaft, two tubes running within the gear housing of the wiper arm towards two washing jets and a lug, via which the line is fastened with screws at the gear housing. The washing liquid line is non-rotatably fastened at the fastening member of the wiper arm, which fastening member is represented by tile gear housing and therefore, also rests in relation to the wiper shaft. Though in case of wiper arms being constructed in the usual way, the proportion of space in the fastening member is so unfavorable, that a form-fitting fastening of the washing liquid line within the fastening member is impossible. Such kind of fixation may also lead to difficulties during the assembly and dismantling of a wiper arm onto or from the wiper shaft.